1. Field of the Invention
One of the aspects of the present invention relates to a process cartridge and an image forming apparatus. The image forming apparatus of the present invention forms an image on a recording medium using electrophotographic image forming process. The image forming apparatus is, for example, an electrophotographic copying machine, an electrophotographic printer (e.g., a light-emitting diode (LED) printer, a laser beam printer), and an electrophotography facsimile apparatus.
The recording medium is a medium on which an image is formed and is, for example, a recording sheet, an overhead projector (OHP) sheet, or the like. Further, the process cartridge is a cartridge having a processing unit and an electrophotography photosensitive drum (hereinafter referred to as a “photosensitive drum”) integrated into one unit detachably attached to the image forming apparatus. The processing unit integrated in the process cartridge is at least one unit out of a charging unit, a developing unit, and a cleaning unit. Thus, a cartridge having at least a developing unit, as the processing unit, and a photosensitive drum integrated into one unit and is detachably attached to the image forming apparatus is included in the process cartridge.
2. Description of the Related Art
A process cartridge detachably attached to an image forming apparatus includes a cleaning unit and a developing unit. The cleaning unit generally includes a photosensitive drum and a cleaning unit. The developing unit includes a developing roller configured to supply developer to a photosensitive drum, a developer supplying unit including a developer supply roller configured to supply the developer to the developing roller, and a developer container which contains the developer.
The developer supplying unit and the developer container are separated by a partition. The partition is provided with an opening to connect the developer supplying unit and the developer container. Through the opening, the developer in the developer container is conveyed to the developer supplying unit by a developer conveyance member provided in the developer container.
When the process cartridge is in the unused state, the opening portion of the developer container is hermetically sealed by a seal member. One end of the seal member is joined to a handle member. When the user mounts the process cartridge to the image forming apparatus main body, the user pulls the handle member to remove the seal member, and the opening portion is opened.
In addition to the above-described configuration, there is proposed a configuration where the seal member is wound after the process cartridge is mounted to the image forming apparatus main body. According to this configuration, a winding member that winds the seal member is provided on the process cartridge. When the winding member receives a drive force from a drive source provided on the image forming apparatus main body, the winding member automatically winds up the seal member and opens the opening portion.
However, if the winding member that winds up the winding member of the seal member and the developer conveyance member are driven by one drive source provided on the image forming apparatus main body, the increase in the load torque of the process cartridge needs to be considered.
Specifically, there are two types of load torque. One is a load torque which is produced when the winding member is driven and the seal member is removed from the opening portion. The other is a load torque which is produced when the developer conveyance member is driven. In the case of the process cartridge in unused state, the developer may be clumped in the developer container due to vibration during distribution. If the developer conveyance member is driven when the developer is clumped in the developer container, a greater load torque than usual will be necessary to unwind the clumped developer.
Considering the load torque, if a drive source that can produce a larger torque is used in the image forming apparatus, the size of the apparatus will be increased or the cost will be increased. Thus, Japanese Patent Application Laid-Open No. 2005-077742 discusses an image forming apparatus which winds the seal member before driving the developer conveyance member when the seal member of the process cartridge in the unused state is wound automatically.
According to such a configuration, the timing of elevation of the load torque due to the winding of the seal member and the timing of elevation of the load torque due to the driving of the developer conveyance member can be staggered. Accordingly, the load of the drive source of the image forming apparatus can be reduced, and thus downsizing of the drive source of the image forming apparatus can be realized. This also leads to downsizing of the apparatus and cost reduction.
However, the conventional configuration has the following drawbacks. Generally, a cleaning unit of a process cartridge includes a cleaning member used for cleaning the surface of the photosensitive drum. The cleaning member is generally a rubber blade which is formed along the longitudinal direction of one end of a sheet metal. The rubber portion of the cleaning member abuts on the surface of the cylindrical photosensitive drum. Further, the cleaning member is arranged such that it abuts on the photosensitive drum in a direction opposite to the rotation direction.
If the photosensitive drum is continuously driven in a state where the developer is not on the contact portion of the photosensitive drum and the cleaning member, slide friction between the photosensitive drum and the cleaning member increases, and burrs may be generated in the rubber portion of the cleaning member.
However, if the image forming apparatus is a type that winds the seal member, the developer is not transmitted to the developing roller until the seal member is wound. Thus, the photosensitive drum will be rotated without the developer between the cleaning member and the photosensitive drum. Accordingly, there is threat that burrs of the cleaning member may be occurred.
Further, if the image forming apparatus is the type described above in which the seal member is wound before the drive of the developer conveyance member, the timing the developer is conveyed to the developing roller by the developer conveyance member further delay. This is further disadvantageous to the generation of burrs of the cleaning member.
Thus, according to the conventional configuration, to prevent the generation of burrs of the cleaning member when the winding of the seal member is performed, a sliding agent is applied to the cleaning member or a material that can reduce the slide friction is used on the surface of the photosensitive drum.